Locator systems are known as radio communication systems used for detecting items (referred to also as “target objects” such as a key, a wallet, a mobile device, and a pet) (for example, Patent Literature 1). A locator system is equipped with a locator attached to an item and a calling apparatus carried around by a user. The locator and the calling apparatus can communicate with each other through near field radio communication. When a user wants to find the item, a user operates the calling apparatus. Upon reception of a radio signal (calling signal) transmitted by an operation of the user, the locator generates a notification sound. With this sound, the user can know that the item is in the direction in which the notification sound is generated.